1. Field
Embodiments of the present invention relate to the fabrication of structures using nano-imprint technology.
2. Background of the Related Art
UV nano-imprint technology is utilized for the fabrication of micro- and nano-structures. Nano-imprint is a mechanical replication technology wherein a mold is pressed into a UV curable resist that was spin-coated on a substrate. UV irradiation of the resist through the mold in the imprinted area leads to the polymerization and curing of the resist. The mold is then removed leaving the inverted three dimensional replica of the pattern formed in the resist. The thin portions of the imprinted resist are removed to create openings in the resist layer, forming a mask that is then utilized to etch one or more layers underlying the resist. This technique enables fast high precision printing down to 10 nm spacing and pattern fidelity to a large extent.
However, most conventional etching processes, such as wet etching that tend to etch isotropically, are not suitable for robustly transferring such small patterns to the underlying material. Particularly, undercutting phenomenon can produce patterned features on the etched underlying material that are not uniformly spaced and do not have desired straight, vertical sidewalls, thereby losing the critical dimensions of the features. Additionally, the isotropic etching of the features may overetch the sidewalls of features in high aspect ratios, resulting in the loss of the critical dimensions of the features.
Plasma etch processing, known as dry etch processing or dry etching, provides a more anisotropic etch than wet etching processes. The dry etching process has been shown to produce less undercutting and to improve the retention of the critical dimensions of the photomask features formed using conventional lithographic techniques with straighter sidewalls and flatter bottoms. However, dry etching may overetch or imprecisely etch the sidewalls of the openings or pattern formed in the resist material used to define the critical dimensions of the underlying layer. Excess side removal of the resist material results in a loss of the critical dimensions of the patterned resist features, which may translate to a loss of critical dimensions of the features formed in the underlying layer defined by the patterned resist. Further, imprecise etching may not sufficiently etch the features to provide the necessary critical dimensions. Failure to sufficiently etch the features to the critical dimensions is referred to as a “gain” of critical dimensions. The degree of loss or gain of the critical dimensions in the metal layer is referred to as “etching bias” or “CD bias”.
Although loss of critical dimension control is of concern in most all etching applications, it is particularly problematic in photomask fabrication. The loss or gain of critical dimensions of the pattern formed in the underlying layer(s) comprising a photomask reticle can detrimentally affect the light passing therethrough and produce numerous patterning defects and subsequent etching defects in substrates patterned by the photolithographic reticle. The loss or gain of critical dimensions of the photomask can result in insufficient photolithographic performance for etching high aspect ratios of sub-micron features and, if the loss or gain of critical dimensions is severe enough, the failure of the photolithographic reticle or subsequently etched device. Since nano-imprint technology can produce very small apertures, conventional etching techniques do not allow effective pattern transfer to the layers underlying the imprinted resist to a degree acceptable for robust photomask fabrication.
Therefore, there remains a need for a process and chemistry suitable for fabrication of structures using nano-imprint technology.